{"id":"CVE-2026-98017","state":"PUBLISHED","title":"net/sched: defer qdisc freeing after failed creation","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: defer qdisc freeing after failed creation\n\nAn RTM_NEWQDISC request can make clsact bind a populated shared ingress\nblock during ->init(), publishing an embedded mini_Qdisc to lockless\nreaders.  If the same request has an invalid TCA_RATE, estimator setup\nfails after ->init(); the unwind removes the pointer but synchronously\nfrees its containing qdisc while tc_run() may still hold it.\n\nRetire failed qdiscs through the same RCU helper as normal destruction.\nInline the synchronous free into the callback now that no direct callers\nremain.","publishedAt":"2026-09-25T10:23:39.107Z","updatedAt":"2026-10-19T09:12:22.590Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"96a27a3e64e7c87abade03fb2ad04ed66992a89a","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"6a1b49bb9fdf9e8e7aa38e8cd635c0cc4074447d","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"20bf6fa34b345333971bd4464a322cce87b83f4e","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"156a3bab69744e9225bb9eff8c5cc53da18d5a2e","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"5bfe927c5b4b290fad529186218c728589b4b101","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"e6662f2100f8d33b0f4d0047c219efd6bba186ea","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_api.c","net/sched/sch_generic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.16","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_api.c","net/sched/sch_generic.c"]}],"references":["https://git.kernel.org/stable/c/96a27a3e64e7c87abade03fb2ad04ed66992a89a","https://git.kernel.org/stable/c/6a1b49bb9fdf9e8e7aa38e8cd635c0cc4074447d","https://git.kernel.org/stable/c/20bf6fa34b345333971bd4464a322cce87b83f4e","https://git.kernel.org/stable/c/156a3bab69744e9225bb9eff8c5cc53da18d5a2e","https://git.kernel.org/stable/c/5bfe927c5b4b290fad529186218c728589b4b101","https://git.kernel.org/stable/c/e6662f2100f8d33b0f4d0047c219efd6bba186ea"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98017.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98017","state":"PUBLISHED","datePublished":"2026-09-25T10:23:39.107Z","dateUpdated":"2026-10-19T09:12:22.590Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:19:56.069Z"},"containers":{"cna":{"title":"net/sched: defer qdisc freeing after failed creation","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: defer qdisc freeing after failed creation\n\nAn RTM_NEWQDISC request can make clsact bind a populated shared ingress\nblock during ->init(), publishing an embedded mini_Qdisc to lockless\nreaders.  If the same request has an invalid TCA_RATE, estimator setup\nfails after ->init(); the unwind removes the pointer but synchronously\nfrees its containing qdisc while tc_run() may still hold it.\n\nRetire failed qdiscs through the same RCU helper as normal destruction.\nInline the synchronous free into the callback now that no direct callers\nremain."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"96a27a3e64e7c87abade03fb2ad04ed66992a89a","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"6a1b49bb9fdf9e8e7aa38e8cd635c0cc4074447d","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"20bf6fa34b345333971bd4464a322cce87b83f4e","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"156a3bab69744e9225bb9eff8c5cc53da18d5a2e","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"5bfe927c5b4b290fad529186218c728589b4b101","versionType":"git"},{"version":"51ab2994c387c80b45caf8b8067b3f3b97771d25","status":"affected","lessThan":"e6662f2100f8d33b0f4d0047c219efd6bba186ea","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_api.c","net/sched/sch_generic.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.16","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/sch_generic.h","net/sched/sch_api.c","net/sched/sch_generic.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/96a27a3e64e7c87abade03fb2ad04ed66992a89a"},{"url":"https://git.kernel.org/stable/c/6a1b49bb9fdf9e8e7aa38e8cd635c0cc4074447d"},{"url":"https://git.kernel.org/stable/c/20bf6fa34b345333971bd4464a322cce87b83f4e"},{"url":"https://git.kernel.org/stable/c/156a3bab69744e9225bb9eff8c5cc53da18d5a2e"},{"url":"https://git.kernel.org/stable/c/5bfe927c5b4b290fad529186218c728589b4b101"},{"url":"https://git.kernel.org/stable/c/e6662f2100f8d33b0f4d0047c219efd6bba186ea"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The trigger is a local rtnetlink RTM_NEWQDISC message (tc_modify_qdisc -> qdisc_create) with a clsact kind, a shared TCA_INGRESS_BLOCK and an invalid TCA_RATE. Packets only drive the reader side (tc_run), and no remote peer supplies the input that causes the bug.\nAC:L - The attacker controls both sides of the race: they repeat the failing clsact create, which runs qdisc_free() with no grace period, while pushing traffic through their own veth/dummy device so that tc_run() dereferences the published miniq. No outside condition is needed.\nPR:L - tc_modify_qdisc only needs CAP_NET_ADMIN in the netns that owns the device, which an unprivileged user gets through unshare -Urn plus a self-created veth/dummy interface. That makes it reachable as PR:L rather than requiring init-namespace root.\nUI:N - The attacker performs every step themselves: creating the shared block and filter, sending the failing RTM_NEWQDISC, and generating traffic. No victim action is needed.\nS:U - The use-after-free and any resulting privilege escalation stay inside the same kernel security authority. No hypervisor or IOMMU boundary is crossed.\nC:H - The mini_Qdisc embedded in the freed qdisc (a kmalloc'd object, so its slot can be reclaimed) is read by tc_run: miniq->block and miniq->filter_list are passed to tcf_classify. With a sprayed replacement object, the attacker controls these pointers, which can be used to leak kernel memory.\nI:H - tc_run calls mini_qdisc_bstats_cpu_update(), which writes through the cpu_bstats pointer taken from the freed object, and tcf_classify follows a filter_list the attacker can control. After reclaim, this gives a controlled write and a path to hijacking control flow.\nA:H - Freeing the qdisc while RCU readers in tc_run still hold its embedded miniq leads to KASAN splats and oopses when the packet path touches the freed or reallocated memory. The result is a kernel crash."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:12:22.590Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.16","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}